Computational analysis of the effect of the control model of intraaorta pump on ventricular unloading and vessel response

The intraaorta pump is a novel left ventricular assist device (LVAD) whose hemodynamic effects on the circulatory system is unknown. This article aims to evaluate the different effects on the circulatory system supported by the intraaorta pump. In this article, the pump is controlled by three control strategies, including the continuous flow method, the constant rotational speed, and the constant pressure head. A cardiovascular pump system, which includes cardiovascular circulation, intraaorta pump, and regulating mechanisms of systemic circulation, has been proposed. Left ventricle pressure (LVP), end-diastolic volume (EDV), and left ventricular external work (LVEW) were used to evaluate the degree of ventricular unloading. The pulsatile index (PI), which is defined as a ratio of pulse pressure and mean arterial pressure (MAP), was used to evaluate the effect of the vessel response by three control strategies. The comparison results showed that LVP and EDV were lower than those measured before the intraaorta pump was implanted. For LVEW, the constant pressure head strategy provided a superior ventricular unloading compared with other strategies. Support of the pump led to the lower pulsatility by the three models. However, the PI of the constant pressure head was the most at 0.37. In conclusion, these results indicate that the intraaorta pump controlled by constant pressure head strategy provides superior ventricular unloading and pulsatility of the vessel.     

股骨头凹及其滋养孔观察

目的：探讨股骨头凹类型与股骨头缺血性坏死的关系。方法：对２５０例正常成人股骨头凹及其滋养孔数目、大小进行了观测。结果：按股骨头凹形态分成五型，按其深度分为三型。股骨头凹滋养孔以单孔最多（３７．２％），无孔次之（２８％），３孔以上较少。滋养孔大小以中孔多见（８２．９５％）。浅平型和凸型股骨头凹Ｘ线片可能不显影，出现无孔的机率明显高于凹型（Ｐ＜０．０１）。结论：浅平型或凸型股骨头凹发生股骨头缺血性坏死的机率可能高于凹型。     

Electron microscopy of cardiac myosin: Its shape and properties as determined by the regulatory light chain

Summary Structural properties of dog cardiac myosin and the influence of the regulatory light chain (LC2) on the shape of myosin heads were investigated by electron microscopy. LC2 was reversibly removed using a neutral protease from myopathic hamsters (Margossian,J. Biol. Chem. 260 (1985) 13747–54). The distribution of myosin head length centred around 17 nm with the mean length being 18.9 nm. Statistical analysis suggested that myosin heads became more globular upon removal of LC2. No extensive aggregation of myosin could be detected after LC2 was dissociated, either by sedimentation velocity or by gels run under non-denaturing conditions. The centre-to-centre distance between heads remained constant at about 21 nm, regardless of the presence or absence of LC2. The distribution of length of the globular region reveals two peaks at 7.5 and 9.5 nm, suggesting an extended and a shorter configuration of this region. The decrease in mass at the head/tail junction upon LC2 removal suggests that it is the binding site for the regulatory light chains. A bend at 57 nm from the head/tail joint was sometimes noticed, corresponding to the myosin hinge region. In high resolution micrographs individual particles revealed invaginations along the contours of the head, possibly delineating the boundaries of structural domains within the head. The conformation of arrowheads in actin decorated with either subfragment 1 (S1) or heavy meromyosin (HMM) was investigated in the presence and absence of LC2.     

A novel patch-field design using an optimized grid filter for passively scattered proton beams

For tumors with highly complex shapes, a 'patching' strategy is often used in passively scattered proton therapy to match the sharp distal edge of the spread-out Bragg peak (SOBP) of the patch field to the lateral penumbra of the through field at 50% dose level. The differences in the dose gradients at the distal edge and at the lateral penumbra could cause hot and cold doses at the junction. In this note, we describe an algorithm developed to optimize the range compensator design to yield a more uniform dose distribution at the junction. The algorithm is based on the fact that the distal fall-off of the SOBP can be tailored using a grid filter that is placed perpendicular to the beam's path. The filter is optimized so that the distal fall-off of the patch field complements the lateral penumbra fall-off of the through field. In addition to optimizing the fall-off, the optimization process implicitly accounts for the limitations of conventional compensator design algorithms. This algorithm uses simple ray tracing to determine the compensator shape and ignore scatter. The compensated dose distribution may therefore differ substantially from the intended dose distribution, especially when complex heterogeneities are encountered, such as those in the head and neck. In such a case, an adaptive optimization strategy can be used to optimize the 'grid' filter locally considering the tissue heterogeneities. The grid filter thus obtained is superimposed on the original range compensator so that the composite compensator leads to a more uniform dose distribution at the patch junction. An L-shaped head and neck tumor was used to demonstrate the validity of the proposed algorithm. A robustness analysis with focus on range uncertainty effect is carried out.     

应用放射造影术进行胰腺头部动脉的三维重建及意义

目的利用应用放射造影术对胰腺头部动脉进行三维重建,为临床手术提供可靠的解剖学依据。方法采用128排螺旋CT对2例新鲜标本进行扫描,并进行三维重建。记录螺旋CT影像下胰腺头部动脉的空间位置关系。结果 2例标本灌注全部满意,管道连续、饱满圆滑、无伪影,构建的数字化胰腺头部动脉可视模型,其形态逼真,能随意旋转、放大和缩小。结论采用聚乙烯醇-氧化铈血管造影术可构建理想的胰腺头部动脉血管网3D可视化模型,为系统研究人胰腺头部动脉血管网的形态结构和血供分布提供了血管解剖学基础。     

Feasibility of the homogeneous head model in the interpretation of neuromagnetic fields

During the past few years it has been demonstrated that active areas in the human brain can be located by measuring the magnetic fields arising from the electric currents in the neurons. An established model for the conductivity geometry of the head in these studies is the layerwise homogeneous sphere. If, however, the measurement grid is too large or the local radius of curvature of the head is changing rapidly in the measurement area, this simple model may become inadequate. In this paper we investigate the feasibility of replacing the conducting sphere by a homogeneous body having the shape of the brain. We show by a semi-quantitative argument that the homogeneous body model is justified. A numerical procedure for the calculation of the magnetic field is presented with examples of the accuracy that can be obtained. An example of significant differences between the predictions of the homogeneous and sphere models is discussed.     

仿活体尸头模型的建立及导航辅助鼻内镜下解剖训练

目的自制仿活体的人尸头解剖模型,利用该模型,进行影像导航辅助鼻内镜下解剖训练,以提高鼻科医生手术技能,加深对影像学的理解。方法首先建立仿活体手术尸头解剖模型。解剖出尸头的颈总动脉及颈内静脉,分别给予仿人体动、静脉血液灌注,使血管内有"血液"充盈。在此模型基础上,影像导航辅助鼻内镜下进行鼻腔、鼻窦及前颅底解剖,首先对各解剖标志进行定位,辨认;当动脉解剖暴露时,可见血管内有血液充盈,受到损伤时,有血液喷出,在此情形下,可进行止血训练,比较接近真实的手术情景。结果 (1)通过对人尸头颈部血管灌注,建立仿活体手术尸头解剖模型。(2)仿活体手术尸头解剖训练达到了接近活体的术野情景。(3)解剖定位准确,加深对影像学的理解。结论仿活体手术尸头解剖模型的建立及影像导航辅助鼻内镜下解剖训练为鼻内镜下解剖训练提供了更加真实有效的方式。     

Skeletal abnormalities in the Apert syndrome

This paper reports on skeletal abnormalities in 38 patients with Apert syndrome. Analysis includes alterations in the shoulders, humeri, elbows, hips, knees, rib cage, and spine (except the cervical spine). Some patients had subacromial dimples and elbow dimples during infancy. Mobility at the glenohumeral joint was limited. Progressive limitation in abduction, forward flexion, and external rotation with growth was virtually a constant finding. The acromioclavicular joint was prominent and sometimes had an angular, pointed appearance clinically. This was often associated with atrophic musculature and winging of the scapulae. Limited elbow mobility was common and usually mild in degree. Decreased elbow extension was most often found with decreased flexion, pronation, and supination occurring less frequently. Limited elbow mobility did not change significantly with growth in contrast to the increasing severity observed in the shoulder joint. Short humeri were a constant finding beyond infancy and genua valga of mild degree were present in many cases. Radiographic examination strongly suggests that the Apert syndrome is characterized by a multiple epiphyseal dysplasia. We found delay in appearance of postnatal ossification centers, particularly in the humeral head, greater tuberosity, capitulum, and radial head. Subsequently, these bones became abnormal in shape. Glenoid dysplasia was observed consistently. The neck of the scapula was very short or absent and the inferior margin of the glenoid cavity was poorly demarcated from the infraglenoid tubercle. The humeral head became oblong in shape with relative prominence of the greater tuberosity which compromised abduction. In the elbow, the capitulum was often small and the radial head was flat in many instances. Subluxation or dislocation of the radial head or angulation of the radial neck was observed in some cases. In the hip joint of some adults, the femoral necks were short and broad with prominence of the greater trochanters. Less common radiographic findings are also discussed. © 1993 Wiley-Liss, Inc.     

Increase in the calculated resistance of anatomically fixed stenosis in vitro in association with decrease in distal resistance

The effects of changes in distal resistance on stenotic resistance were studied in vitro. Physiological saline was passed through the left carotid artery obtained from the dog, flexible rubber tubing, or through solid polyethylene tubing with a constant perfusion pressure or with a constant flow rate. Various stenotic resistances were established using a screw type constrictor and the distal resistance was varied by allowing physiological saline to pass through either a 23 gauge hypodermic needle (high peripheral resistance) or 23 and 20 gauge needles (low peripheral resistance ). For arteries with anatomically fixed stenosis, the calculated resistance was increased in association with reduction of the distal resistance. The stenotic resistance in the flexible rubber tubing changed in the same manner as that of the carotid artery, while the solid polyethylene tubing showed no significant stenotic resistance changes due to altering the distal resistance. These findings suggest that the stenotic resistance change of the artery correlates with the elasticity of the vessel wall and also indicate that resistance values were of little usefulness for evaluating the effects of vasodilating stimuli on the vessel segment with a significant stenosis.     

Efficient sampling in 3-D stereologic volumetry

Present 3-D stereology techniques use fixed grid sampling where the sampling grid of test points is randomly placed in 3-D. In order to increase randomness of sampling, in this paper we propose random grid sampling scheme where grid sections are placed randomly over 2-D cross-sections. A random grid sampler has superior efficiency and accuracy compared with fixed grid sampling. Using MR head scans we demonstrate the use of random grid sampling in volumetry of structures in 3-D biomedical images.     

Simulation of steady cardiovascular flow in the presence of stenosis using a finite element method

Stenosis could affect one or more segments of the human cardiovascular system. It is a problem capable of causing grave effects. In the present study, the finite element method has been utilised to construct a computer simulation model for the human cardiovascular system in which one or more blood carrying elastic segments are affected by stenosis. Computational effects on the effects of stenosis in aorta arch, carotid, and coronary arteries on parameters of steady flow through the system are presented. It is found that when the total flow rate through the heart is maintained constant, the most notable effect is a very marked increase in pressure drop occurring over the length of the vessel affected with stenosis. Pressure drop in many other segments also increases but by a much smaller extent. On the other hand, when the pressure at the inlet of the ascending aorta and the outlet of the vena cava are maintained constant, the most marked effect is a decrease of flow rate through the stenosed vessel. Stenosis not only causes a pressure drop in the affected segments but it also changes pressures at points distal from the site of stenosis. It also causes a redistribution of flow through the cardiovascular system.     

股骨头内吻合断裂支持带动脉重建血供的可行性研究

目的 探究模型动物股骨头内吻合断裂支持带动脉重建血供的可行性。 方法 选取20例成年家猪髋关节标本,用硫酸钡悬液通过囊外动脉环对股骨头进行灌注,观察各支持带动脉的分布及入股骨头后的走行特点。另20例标本建立头下型股骨颈骨折模型后,在股骨头表面凿一个三角形骨槽,显露头内最粗支持带动脉与股骨颈侧的血管断端进行端端吻合。用硫酸钡悬液检测吻合血管的通畅情况和股骨头的灌注情况。 结果 20例灌注标本可观察到有3组支持带动脉为股骨头供血,各支持带动脉入头后的起始部分沿皮质下走行。向20例头下型股骨颈骨折模型动物的头内吻合的支持带动脉灌注硫酸钡悬液,均能顺利通过吻合口且在持续灌注后股骨头内的其它动脉均有硫酸钡悬液充盈。 结论 股骨头内吻合断裂支持带动脉的方法可行,可以恢复股骨头血供。     

The arteries of the humeral head and their relevance in fracture treatment

Bone vascularisation has gained increased interest in relation to the blood supply of bone fragments during treatment of fractures. In the current study the pattern of vascular supply of the proximal humerus was studied in six cadavers by the corrosion technique. Furthermore, the effect of fractures on the vascular supply was also investigated. In all preparations the intraosseous arteries of the humeral head arose from the circumflex arteries, which surrounded the humerus and dispatched branches towards the proximal end. The main vessel was the branch of the anterior circumflex artery, penetrating the major tubercle in six of six cases. Due to the intraosseous arch shape of this vessel it is referred to as the arcuate artery. Besides other smaller vessels, there was also a vascular network arising from the posterior circumflex artery. Their branches penetrated medially at the cartilage bone interface in five of six preparations. The medial bone arteries appear to gain distinctive importance in humeral head fractures by their impact on the vascularisation of the fracture fragments. After disruption of the arterial supply from the arcuate artery, the vascularisation of the head fragments is most likely ensured by this group of vessels. Therefore, necessary repositioning manoeuvres during open reduction of the fracture should be conducted with care in order to preserve these arteries.     

Mechanical behavior of pressurized in vitro prearteriolar vessels determined with a video system

The muscular resistance arteries of the mesentery and brain serve two different control functions in the cardiovascular system. The former are representative vessels of vascular beds that influence total peripheral resistance and blood pressure; the latter are a good model of vessels in beds that demonstrate blood flow autoregulation. Our purpose was to develop a versatile myographic system appropriate for the in vitro study of 75–250 μm diameter vessels and to explore different physiological properties of cerebral and mesenteric arteries. In this paper the system is described in detail, examples of its use in determining the dynamic responses of the vessels to electrical stimulation are provided, and certain measures indicative of the extent of myogenic behavior are characterized. Cylindrical artery segments about 3-mm long were dissected from Wistar-Kyoto rats and mounted in a chamber filled with physiological saline solution maintained at 37°C. The same solution was perfused via a syringe into one end of the vessel through a microcannula. The other end was then occluded so that experiments could be made over a wide range of transmural pressures without flow. The vessel was viewed through a microscope coupled with a TV camera, and the video output signal of a selected scan line was processed by an electronic dimension analyzing system. This permitted simultaneous digital presentation and analog voltage outputs of the vessel wall thicknesses and lumen diameter. We further incorporated servo control of the syringe using a motor drive. In this way, vessel tests could be carried out at constant pressure or constant diameter, and vessel responses could be obtained following either pressure or diameter command signals. Using the methods presented in this study, small vessels can be maintained under conditions that approximate their in vivo state more closely than other in vitro techniques using ring segments on wires. We also find that the opto-electronic instrumentation is ideally suited for studying the dynamic vessel properties that underlie the control of vascular smooth muscle.     

First-order system least-squares (FOSLS) for modeling blood flow

The modeling of blood flow through a compliant vessel requires solving a system of coupled nonlinear partial differential equations (PDEs). Traditional methods for solving the system of PDEs do not scale optimally, i.e., doubling the discrete problem size results in a computational time increase of more than a factor of 2. However, the development of multigrid algorithms and, more recently, the first-order system least-squares (FOSLS) finite-element formulation has enabled optimal computational scalability for an ever increasing set of problems. Previous work has demonstrated, and in some cases proved, optimal computational scalability in solving Stokes, Navier-Stokes, elasticity, and elliptic grid generation problems separately. Additionally, coupled fluid-elastic systems have been solved in an optimal manner in 2D for some geometries. This paper presents a FOSLS approach for solving a 3D model of blood flow in a compliant vessel. Blood is modeled as a Newtonian fluid, and the vessel wall is modeled as a linear elastic material of finite thickness. The approach is demonstrated on three different geometries, and optimal scalability is shown to occur over a range of problem sizes. The FOSLS formulation has other benefits, including that the functional is a sharp, a posteriori error measure.     

Calculation of dose and contrast for two mammographic grids.

To aid in selecting optimal conditions for screening mammography practice in Sweden, the performance of two mammographic grids (one moving and one stationary) has been investigated. Monte Carlo techniques were used to simulate photon transport in the breast. Transport through the breast support, grid covers, grid and image receptor (33.9 mg cm-2 Gd2O2S) was treated analytically. The contrast of a 100 microns calcification has been evaluated for three tissue compositions (adipose, glandular, 50:50 fractions by weight of adipose and glandular tissue) as a function of breast thickness (2-8 cm) and potential difference (25-30 kV, Mo anode). Contrast for a 5 cm 'average' breast at 28 kV was improved by 40% using the moving grid and by 30% using the stationary one; the corresponding increases in breast absorbed dose, keeping the energy imparted to the image receptor constant, were 90% and 150%, respectively. The superior properties of the moving grid were due to (i) equal scatter rejection ability and higher transmission of primary photons yielding lower scatter-to-primary ratios behind the grid, and (ii) less attenuation and filtering of the primary photons in the interspace material yielding lower degradation of primary contrast.     

Effect of impact on different regions of the head of lambs

The heads of anaesthetized lambs aged 4-5 weeks were subjected to impact (temporal, frontal or occipital) of constant strength with a humane stunner. Two hours later, the brains were perfusion-fixed with 4% paraformaldehyde and serial whole coronal slices processed by routine methods. Sections were stained with haematoxylin and eosin or labelled with a monoclonal antibody to amyloid precursor protein, a sensitive marker of axonal injury and neuronal reaction. Microscopical evaluation of axonal, neuronal and vascular damage was performed with a quantitative grid system. Frontal impact produced the greatest damage, followed by occipital then temporal impact. An unusual lesion found in the majority of lambs subjected to impact was multifocal necrosis of the cerebellar granular layer. The findings should assist clinicians in evaluating the probable outcome of traumatic head injury in domestic animals. Copyright Harcourt Publishers Ltd.     

股骨头颈骨内、外静脉回流的解剖学研究

目的 :为探讨Legg Perthes病的发病机理及临床治疗提供形态学依据。 方法 :采用巨微解剖、血管透明、组织切片、造影、扫描电镜等方法对 45例胎儿、新生儿及儿童的股骨头颈骨内、外静脉回流途径、骨内微血管构筑特点进行观察。结果 :(1 )髋关节骨外静脉包括 :旋股内、外侧静脉 ,闭孔静脉 ,臀上、下静脉 ,颈后静脉 ,髂腰静脉 ,股骨头韧带静脉 ,颈升静脉 ;骨内静脉包括 :前、后、上、下骺静脉 ,内骺静脉 ,前、后、上、下干骺静脉。关节囊内存在丰富的滑膜下静脉网 ,髋关节周围形成两个彼此有吻合的环状结构。(2 )一条微动脉一般有两条微静脉伴行 ,微静脉间有丰富的横行吻合支 ,在微动脉移行为毛细血管的部位 ,常可见到环形缩窄。结论 :(1 )Legg Perthes病与股骨头、颈静脉回流障碍密切相关。 (2 )根据股骨头、颈骨内外静脉回流特点 ,Legg Perthes病可以设计骨内、外双重介入治疗 ,骨内、囊内静脉搭桥的显微外科治疗方案     

The development of astrocytes and blood vessels in the postnatal rabbit retina

Summary Antibodies to glial fibrillary acidic protein (GFAP) have been used to study the shape and location of astrocytes in whole mount preparations of developing postnatal rabbit retina. At all developmental stages GFAP-positive astrocytes were detectable. At birth, they were few in number and only weakly labelled. With further development, their number as well as their labelling intensity increased. Following Nissl counterstaining it was observed that GFAP-positive astrocytes, always situated in the nerve fibre layer, are capable of cell division during about the first 4 postnatal weeks.GFAP-positive astrocytes were always confined to a wing-shaped area extending horizontally from both sides of the optic nerve head. It is suggested that astrocytes are not generated in the entire rabbit retina, which is in clear contrast to the second glial cell type of the rabbit retina, the Müller cell; and it has been concluded that the confinement of astrocytes to the medullary rays region in the adult rabbit is established during ontogenesis, and is not due to a secondary restriction of astrocytes to this region.Horizontal sections cut through entire rabbit retinae at various postnatal stages revealed that the first intraretinal blood vessels are not found before postnatal day 9. This is more than 1 week later than the first astrocytes are detectable. It is suggested that, at least in the rabbit, retinal astrocytes do not co-migrate with blood vessel endothelial cells from the optic disc into the retina, a hypothesis considered recently for the cat retina.It was, however, not possible to decide unequivocally if, in this material, astroglial progenitors are derived from retinal neuroepithelial cells or invade the retina from the optic nerve head.     

An Algorithm for Tracking Microcatheters in Fluoroscopy

Currently, a large number of endovascular interventions are performed for treatment of intracranial aneurysms. For these treatments, correct positioning of microcatheter tips, microguide wire tips, or coils is essential. Techniques to detect such devices may facilitate endovascular interventions. In this paper, we describe an algorithm for tracking of microcatheter tips during fluoroscopically guided neuroendovascular interventions. A sequence of fluoroscopic images (1,024 × 1,024 × 12 bits) was acquired using a C-arm angiography system as a microcatheter was passed through a carotid phantom which was on top of a head phantom. The carotid phantom was a silicone cylinder containing a simulated vessel with the shape and curvatures of the internal carotid artery. The head phantom consisted of a human skull and tissue-equivalent material. To detect the microcatheter in a given fluoroscopic frame, a background image consisting of an average of the four previous frames is subtracted from the current frame, the resulting image is filtered using a matched filter, and the position of maximum intensity in the filtered image is taken as the catheter tip position in the current frame. The distance between the tracked position and the correct position (error distance) was measured in each of the fluoroscopic images. The mean and standard deviation of the error distance values were 0.277 mm (1.59 pixels) and 0.26 mm (1.5 pixels), respectively. The error distance was less than 3 pixels in the 93.0% frames. Although the algorithm intermittently failed to correctly detect the catheter, the algorithm recovered the catheter in subsequent frames.